I just bought a house on a piece of subdivided farm property. It appears that the original farm cistern sits on the upper side of my hilly property. I had lots of flooding in my back yard this spring, even after the May/June showers subsided. I believe this old cistern had something to do with it so wondered what the best way to either remove the problem for next year. Should I fill it with sand? Dismantle it? (it's approx 6X12 concrete structure)? do I need to involve the local EPA?